Urban Forest Management

The City of Toronto maintains planted, naturalized areas through best management practices such as forest thinning, prescribed burns and controlling invasive plant species. Those practices create healthy forests that provide many environmental benefits. Learn how you can help and what to expect when forest management operations are happening in your area.

Pollution, construction, erosion and other factors deteriorate our natural habitats, and invasive species take advantage of the disturbance to thrive. Invasive species compete with native plants for growing space and nutrients. Please keep in mind that Invasive species management on public land is done by UF qualified staff only.

Cosmetic use of pesticides is prohibited unless authorized by a permit from Ministry of Environment, Conservation and Parks.

The city completed another successful prescribed burn in High Park on April 23, 2018. View a map of the burn sites.

A prescribed burn is a deliberately set and carefully controlled fire. It burns low to the ground and consumes dried leaves, small twigs and grass stems but does not harm larger trees. It encourages the growth of native savannah vegetation and sets back the growth of undesirable invasive species.

Prescribed burns are:

Planned and lead by a highly trained Fire Boss.

Controlled by the Fire Boss and a trained crew so the prescribed burn:

progresses at a walking pace

removes invasive/exotic species

remains under control

Used on small areas of land to ensure the survival of habitats for birds, butterflies and insects.

During burns:

onsite City staff provide information about the burn and ensure public and wildlife safety

park users should be prepared for restricted access to areas near burn sites, including temporary road closures, trail closures and reduced parking

smoke from burns will rise and dissipate in ideal conditions, however, weather changes could cause smoke to drift and impact residential areas near the park(s)

close windows or consider leaving the area to avoid potential sensitivity to smoke

Why we have prescribed burns

Toronto is home to the rare black oak savannah ecosystem. Only 1% of this ecosystem remains after human settlement. This ecosystem can be found in High Park, Lambton Park and South Humber Park.

High Park contains about 23 hectares of fragmented black oak savannah and is the most significant area of the savannah ecosystem in Toronto.

Wildfires are a natural occurrence in savannah ecosystems and savannahs have evolved to be fire-dependent. Prescribed Burns are designed to mimic wildfires and benefit native plants and animals by removing invasive/exotic plants and grass, restoring wildlife habitat and returning nutrients to the soil.

Access to the park(s) and its facilities may be limited during a tree thinning. Trails will be cleared of debris but most downed trees will remain to decompose and contribute to the health of the forest.

Tree thinning is a selective removal of trees and shrubs from a densely planted area so that the remaining trees will have better access to growing space, light, water and other nutrients.

During a tree thinning:

downed trees will be left behind to decompose unless doing so will be unsafe or cause problems

most sites will be replanted with new native trees and shrubs

invasive/exotic plants will be prevented by the use of herbicides

signs will be posted if herbicides are used

Sites may look different after tree thinning.

Why tree thinning is done

Succession is the natural process of replacement of one group of plants by another group of plants in an area over time. Species that are more tolerant to shade will naturally replace the species that are fast-growing and less shade tolerant.

Tree thinning mimics succession. In the City of Toronto, thinning will be implemented in the areas that were densely planted with a mix of sun and shade-loving trees. Short-lived, sun-loving trees such as poplars provided habitat for the growth of long living, shade-loving trees such as oaks and maples.

Once the long living species become well established, the short-living species are removed to reduce the competition for growing space and promote the growth of the shade-loving species.

The Ontario Ministry of Environment, Conservation and Parks Cosmetic Pesticide Ban limits the use of pesticides by homeowners for cosmetic uses. There are exceptions for forestry management, arboriculture, health and safety, and natural resource management. Application of pesticides under these exceptions will require the services of a licensed exterminator.

The City of Toronto uses herbicides under the natural resources management exception to manage larger areas infested by aggressive invasive species that can’t be managed manually.

Roundup Weathermax is the primary herbicide used by the City. It is considered non-toxic.

Garlon RTU is used for species that don’t respond to Roundup Weathermax. It is particularly good for roots. This herbicide can also be used in colder weather. It has a low-toxicity.

Coloured dye is mixed with the herbicides to indicate where it has been used. City staff will post signs indicating the area that has been treated. Please follow the instructions on the signs until they have been removed.

Pesticide use is regulated. Any use of pesticides (including herbicides) is prohibited in the city of Toronto and homeowners shall focus on manual methods of invasive species management.